# QUALITY ASSURANCE SUMMARY FOR

**MONTANA TEST OF CES’s CEM**

**1.0. INTRODUCTION**  Cooper Environmental Service’s (CES) **X**

- ray-based **C** ontinuous **E** missions **M** onitor (XCEM) extracted an isokinetic sample from the test duct through a one

inch diameter nozzle. This stack gas sample was slowed in a downward

- flow stilling chamber where a second isokinetic sample was drawn through a test filter tape that trapped both particulate and ionic vapor

- phase elements. The entire sample extraction system was heated to about 350°F. The sample anal yz ed by the X

- ray fluorescence anal ysis part of the XCEM consisted of a spot with a diameter of about 0.25 inch, which was positioned near the center of the X

- ray excitation beam. There are two parameters (elemental mass and volume) that go into the calculation of stack gas concentrations, but there are four categories for potential errors in this measurement: sample extraction efficiency , filter sampling efficiency , elemental mass determination, and measurement of stack gas volume sampled. **Sample Extraction** . The sample extraction system was designed to minimize loss of particulate due to impaction and settling. The use of a one

- inch diameter nozzle made the extraction system relatively insensitive to flow variations. The stilling chamber was three inches in diameter and three feet long. The stilling chamber meets the eight diameter rule and previous tests of a similar stilling chamber has shown that the particle concentration at the test sample extraction point is uniform to within ±3%. Although there is bound to be some loss of particles and gaseous species to the walls of any extractive CEM, these losses can be minimized and the results adjusted for these small losses. In this particular test, the particulate losses prior to filter sampling appear to be less than about 10%. This estimate is based on the following reasons:

 Only about 10% of the Method 29 metals were deposited in the much smaller Method 29 nozzle and transport tubing.

 The average reported lead and chromium concentration s are 8% and 11%, respectivel y, less than the Method 29 concentrations. The arsenic, cadmium, chromium and lead concentrations after adjusting for calibration errors are onl y a couple of percent lower than the corresponding Method 29 results. Assuming similar particle size distributions for the other elements, it is unlikely

that particle loss in the XCEM extraction component is a significant source of error.

 The potential loss of gaseous species is expected to be low because the addition of chlorine gas resulted in the increase in only lead, and then onl yabout one microgram. If other potential vapor phase species had been lost to the walls, the high temperatures and chlorine gas is expected to indicate this as it did with the small amount of lead.
**Filt er Sampling Efficiency**  . The filter sampling efficiency has been determined in the laboratory

to be on the order of 98% for particulate and ionic vapor phase elements. Elemental vapors such as mercury have trapping efficiencies of less than 1%. The original test plan called for the addition of chlorine gas to convert the elemental mercury

to mercuric chloride, which would then be trapped by the filter. Because of s ys tem problems, chlorine gas was used onl y for a few samples. Thus, the XCEM low reported mercury results are expected to be due to the presence of elemental mercury and its poor sampling efficiency . The Method 29 results suggest that the other metals were dominated by particulate species. Thus, the sampling efficiency

is not expected to have contributed to differences in the XCEM and Method 29 results.
**Elemental**
**- Mass Determination**  . The elemental mass in the filter deposit was determined using an energy

- dispersive X

- ray fluorescence analyzer. This method is a particularl y powerful tool for this application because the anal ys is is non

destructive and its results are potentiall y National Institute of Standards and Testing (NI ST) traceable. In addition, the spectral results for each analysis are recorded, all of the elements are determined simultaneously , the elemental sensitivities are a smoothly varying function of atomic number, and the elemental anal yz er is extremely

stable, ty pically requiring recalibration only about once or twice a ye ar. In this particular evaluation, the instrument was calibrated prior to the field tests, but the calibration could not be validated before the tests because of limited time. However, post calibration tests were conducted and indicated less than a 3% change in the calibration. Additional post calibration tests did indicate a bias in the XCEM calibration factors, which can explain most of the difference in the reported XCEM and Method 29 concentrations for arsenic, cadmium, chromium and lead concentrations. If the independent laboratory based XCEM calibrations factors are used, arsenic, cadmium, chromium and lead would all meet the EPA relative accuracy criteria of 20%. These adjustments are discussed in Section 4.0. **Volume Sampled** . The volume of stack gas sampled was determined by subtracting the diluti on gas volume from the total sample volume determined by a NI ST

- traceable mass flow meter. In the earl y part of the tests, the dilution volume was estimated with a rotameter, which was subsequently calibrated against the mass flow meter. In the latter po rtion of the tests, a second mass flow meter was used to determine the dilution gas used. In general, uncertainties in the stack gas volume sampled are not expected to have contributed significantly

to any of the differences in the Method 29 and XCEM re sults. This is based on the fact that the same volume is used in the calculations for each of the elements. Since the chromium and lead were very close to theMethod 29 results, the volume used in the calculations for all the elements could not be signif

icantly in error with either of the two methods. 

### 2.0. **PRE**
**- TEST LABORATORY DETERMINATIONS**  **2.1. Energy calibration**  The X

- ray

fluorescence analyzer component of the XCEM is periodically calibrated for energy . During this evaluation, the instrument was calibrated for energy prior to calibrations, and the online field tests.
**2.2. Determination of elemental line interferences**  Elements expected to be present in the test stack gas were determined from filter samples collected at the test facility . The analyzer was calib rated for these elements and potential spectral interferences determined. The elements present in the stack gas during the tests were as determined from the pre

- test samples.
**2.2. Blank interference and variability determinations**  Blank filter tape elemental c oncentrations were determined prior to the tests and during the online field tests. In no case, was there a measurable amount of the reported elements present in the blank tape, nor was there a significant amount of a potentially

interfering element. The only major elements present were sulfur and chlorine. The only

measurable trace element impurities were a few nanograms per cm2 of iron, zinc and bromine.
**2.3. Elemental sensitivity determination**  The anal yz er elemental sensitivities or calibration factors were determined using thin

- film standards (Micromatter), which are NI ST traceable through gravimetric standards. These standards were internally evaluated by

plotting elemental sensitivities versus atomic number. Because the electron binding energies and probabilities for creating electron vacancies is a smoothly vary function of atomic number, any elemental sensitivity falling off a best

- fit smoothly varying curve was considered suspect and evaluated. The calibration factors used to calculate the origin all y reported results were based on these thin film standards. These factors were subsequently adjusted based on post anal ys is of XCEM spots by an independent analy

tical laboratory

as discussed in Section 4.0. Mercury was an exception to this procedure. Thin film mercury standards are not available. For these tests, a secondary mercury sample was used for spectral response calibration and a theoretical instrument ratio to lead was used to calculate a mercury

intensity calibration factor. The instrument s manufacturers theoretical ratio of 0.85 was used. This ratio has not yet been validated, and may be a source of some of the differences in the XCEM

- reported results. 

### 3.0. **PRE**
**- TEST ONLINE QUALITY ASSURANCE TESTS**  **3.1 Energy calibration** The XCEM was energy calibrated prior to the tests after it had been installed in the test facility . This energy calibration was checked periodicall y during the test period.
**3.2 Elemental sensitivity check**  The elemental sensitivity or calibration factors were checked at the site after system installation and just prior to the test runs by anal yz ing the thin film calibration standards as unknowns. The resulting XCEM results are compared to post

- tests XCEM results in the following section. This comparison shows that instrument calibrati on drift was less than 3% between the online field application and post

- test laboratory

measurements over a month after the field tests.



### 4.0. **POST TEST LABORATORY QUALITY ASSURANCE TESTS**
The XCEM was disassembled after the online field tests and reassembled at CES’s laboratory

several weeks later. Several post

- test quality assurance checks were conducted at this time. The results of these post quality assurance tests are discussed in the following subsections.
**4.1. Energy calibration check**  The system was calib rated for energy prior to instrument use to assure proper peak shape and location in the recorded X

- ray spectra. **4.2. XCEM analysis of thin film standards as unknown**  Thin film standards were used to calibrate the XCEM prior to online anal ysis. These same thin film standards were run again as unknowns prior to the online tests assuming a sample volume of 0.01 m 3 . After the XCEM was returned to the laboratory , these thin film standards were again analyzed as unknowns as a post calibration check. The pre

- test and post

- test equivalent stack gas concentrations reported b y the XCEM are compared below.

In

- field In

- lab Pre

- test results Post

- test results Difference Element μg/m3 μg/m3 μg/m3 Percent Sb 2541 2515 26 1.0 Pb 3108 3056 52 1.7 As 2044 2003 41 2.0 Cd 1510 1550

- 40

- 2.6 Clearly , there had not been a significant change in the XCEM calibration since the system was in use at the Montana tests and reassembled at CES’s laboratory

. This is important because the subs equent laboratory tests and potential adjustments of the field data rel y on this determination that there has been no change in the elemental calibration factors since the online field tests.**4.3. XCEM reanalysis of selected XCEM field test samples**  Seven XCEM deposit spots from the online field tests were reanal yz ed in CES’s laboratory . This was done to validate the online field test results and to assure the deposits had not lost a significant amount of mass when they came in contact with tape on the spool. The results of the laboratory analyses are compared with the online field test results in Table 1. The average difference between the laboratory and field measurements was 1.9%, with the laboratory results generall y less than the field test results. This confirms the field measurements to an uncertainty of about 6% and suggests that possible loss of deposit mass was reasonabl y small. Four of these spots were submitted to Chester LabNet for GFAA (graphite furnace atomic absorption) anal ys is of arsenic, le ad and cadmium (There was insufficient sample to analyze for antimony and chromium.), and two additional deposit spots were analyzed by CVAA (cold vapor atomic absorption) for mercury . The results from these anal ys es are discussed in the following subsection.
**4.4. AAGF/CVAA analysis of selected XCEM field test samples**  The seven selected deposit spots analy zed above were submitted to an independent laboratory

(Chester LabNet) for wet

- chemical analysis. Because of the small deposit mass, all of the reported e lements could not be anal yz ed in each of the spots as noted above. The results of post

- test wet chemical anal ys es of the selected deposit spots from the field tests are summarized in Table 2. This table shows that there is no significant difference in the lead concentrations measured by the independent laboratory

and measured at CES’s laboratory . There was, however, significant differences in the two laboratory results for Hg, As, and Cd. The average difference for two mercury spots was 28%. This sug gests that the mercury reported b y the XCEM was low by , on average, 28%. This is not necessarily surprising since a theoretical sensitivity factor was used because of the absence of available mercury

standards. The mercury

results, however, would still b e low relative to Method 29 results even with a 28% adjustment because of the low filter trapping efficiency

for elemental mercury

. In the case of cadmium, the average difference in the laboratory XCEM results and the independent laboratory reported cadmium results is 17%. If the independent laboratory

results were assumed to be the best representation of the true cadmium mass, the online XCEM calibration factor and field results would need to be increased b y 17 %. With this adjustment, the average XCEM field test cadmium results would be in good agreement with the Method 29 cadmium results; that is, 98 μg/m 3 versus 100 μg/m 3

. The independent laboratory arsenic results also suggest an average XCEM calibration bias of 24%. Again, if the independent laboratory results assumed to be the best representation of the arsenic mass in the XCEM spot, the XCEMarsenic calibration factor and field results would need to be increased by 24%. Again, with this adjustment, the average XCEM arsenic results are in good agreement with the method 29 results, 25 μg/m 3 for Method 29 versus 21 μg/m 3 for the XCEM. The good agreement for the independent laboratory and XCEM laboratory lead results is strongl y supportive of the online field XCEM results. The XCEM results would be a couple of percent closer in agreement with the Method 29 results if the independent laboratory lead results were used to adjust the XCEM calibration factor for lead. With this adjustment, the average XCEM lead is 67 μg/m 3 compared to 70 μg/m 3 for Metho d 29. The antimony

results, however, differ b y more than five fold. There was insufficient sample available for the determination of chromium and antimony on the spots submitted for independent anal ys is. However, it is clear at this time that the reported Method 29 antimony results are grossly

in error and probabl y due to poor recovery

of antimony

in the anal ytical laboratory . This conclusion is based on the generally

good agreement between the two methods (after adjusting calibration factors) for arsenic, cadmium, chromium and lead, the higher XCEM results, and the XCEM measured antimony to cadmium ratio. The good agreement for these four elements strongl y validates the volumes used in both methods. Thus, the antimony difference cannot be explained by a difference in the volumes used to calculate the antimony concentration. The fact that the XCEM results are about six

- fold greater than the Method 29 results implies that the difference is not due to loss of antimony in the XCEM. However, there is a w ell

- established potential for loss of antimony in some EPA filter digestion procedures such as EPA Method 3050, SW 846. In addition, the XCEM results show that the antimony stack gas concentration is clearl y almost two times greater than the cadmium c oncentration, not almost six times less than the cadmium concentration as suggested by the Method 29 results. Since the cadmium results are in good agreement, the difference in the elemental ratio must be associated with the antimony . Because the XCEM me asures the antimony and cadmium simultaneously , its measure of the ratio is highl y reliable and expected to have an uncertainty of no more than about 10%. In addition, since the spectra for each sample spot was saved, they were reviewed and the anal yt e line intensities and reported relative concentrations were confirmed. Additional spots have been submitted to an independent laboratory for antimony and cadmium determinations. These results will contribute significantl y to our understanding of the differences in reported antimony resultsThus, for the above stated reasons, it is highl y likely that the Method 29 results are in error due to loss of antimony , most likely through either volatilization or in the filtered precipitate prior to instrumental anal ys is.
Itis also important to note that this ty pe of post

- independent laboratory analysis is possible because of the nondestructive nature of the XCEM anal ys is and the above

- demonstrated minimal loss of deposit to other portions of the tape on the spoo l. The comparison of results is essentially equivalent to a pre

- anal ys is spike recovery test. The primary

limitation of this ty

pe of post

- test anal ys is recovery evaluation is the anal ytical sensitivity and accuracy

of the method used by

the independent l aboratory

. **4.5. XCEM analysis of spikes**  In addition to the above quality assurance steps, a post

- test analysis of spiked filter samples was conducted. The resulting calibration factors using spikes for arsenic, cadmium, lead and antimony are generally

supportive of the above conclusions.

**Table 1. Comparison of Online Field Test Results with Post-Test Lab Results CES**  **Lab Field**  **% Diff CES**  **Lab Field**  **% Diff CES**  **Lab Field**  **% Diff CR**  **CR CR**  **HG HG**  **HG AS**  **AS AS**  64 39 34.0 34.4 -0 .9 19.4 21.3 -9.4 22.3 15.4 36.3 65 40 32.7 37.7 -14.2 20.6 20.8 -0.9 23.5 25.7 -8.8 66 41 36.4 31.6 14.2 19.7 20.5 -3.9 22.2 19.8 11.5 67 42 36.5 36.7 -0 .5 19.9 23.2 -1 5.1 22.4 18.5 18.9 68 43 30.4 31.2 -2 .5 18.9 18.7 1.4 18.7 20.4 -8.6 69 44 31.9 28.7 10.6 15.7 20.8 -2 8.3 21.9 18.6 16.1

**33.7 33.4**  **1.1 19.0**  **20.9 -9.4**  **21.8 19.8**  **10.9**

**CES Lab**  **Field % Diff**  **CES Lab**  **Field % Diff**  **CES Lab**  **Field % Diff**  **PB PB**  **PB CD**  **CD CD**  **SB SB**  **SB** 64 39 98.1 95.2 3.0 109 118 -8.0 197 211 -6.9 65 40 98.0 108.2 -9 .9 110 118 -7.5 208 211 -1.2 66 41 96.1 101.4 -5 .4 106 105 0.5 193 188 2.9 67 42 97.9 114.1 -15.3 111 111 -0.2 211 196 7.3 68 43 87.2 97.6 -11.2 97 104 -7.3 188 205 -8.4 69 44 86.0 92.5 -7 .3 94 95 -0.5 169 185 -9.3

**93.9 101.5**  **-7 .7**  **104.4 108.6**  **-3.9 194.3**  **199.2 -2.6**  **Average Overall**  **XRF Run 12/9/99** 

**Run No.**

**Overall XRF Run**  **12/9/99**

**Run No. Average** **Table 2. Comparison of XCEM Results (In CES lab) With Independent Lab Results**

**XCEM a**  **AA b**  **% Diff. XCEM**  **a AA**  **b % Diff.**  **XCEM a**  **AA b**  **% Diff. XCEM**  **a AA**  **b % Diff.**  **63** 24 35 33 **64** 15 23 32 118 143 18 95 100 4 **65** 26 30 16 118 140 16 108 108 0 **66** 20 25 20 105 129 18 101 103 2 **67** 19 21 12 111 130 14 114 111 -3 **68** 20 35 41 104 125 17 97 105 7 **69** 24 31 23 **Mean** 20 27 24 111 133 17 103 106 2 24 33 28 **SD** 4 6 12 7 8 2 8 4 4 0 3 7 **Range** 15-26 23-35 104-118 125-143 95-108 100-111 24 31-35 **a) Reported final corrected concentrations b) Concentrations based on elemental mass determination by GFAA for As, Cd and Pb, and CVAA for Hg**  **Hg Run**  **As Cd**  **Pb**